Evaluating High Biomass Sorghum Yields and Nitrogen Use Efficiency in Missouri.

Demands for high-yielding, alternative biofuel feedstocks elicits the need to fully evaluate high biomass sorghum (Sorghum bicolor (L.) Moench) yield response and nitrogen use efficiency (NUE) to varying N fertilization rates in the U.S. Midwest. The objectives of this study were to determine the optimum N fertilization application rates and nitrogen removal response for the production of two high biomass sorghum cultivars (ES5200 and ES5201) over two years in central Missouri. The effects of five rates of N fertilizer (0, 56, 112, 168, 224 kg ha-1 N) were tested on dry matter (DM) yields, and theoretical lignocellulosic ethanol yield and stem-leaf dry matter ratios. Dry matter nitrogen content was used to determine NUE and nitrogen recovery efficiency (NRE) at each N rate. Nitrogen (N) rate was significant both years for dry matter yields and ethanol with no additional N benefit above 56 kg ha-1. Total dry matter yields averaged 12.8 Mg ha-1 and ethanol averaged 3,999 L ha-1 across years, with stem DM more than double leaf DM. An average of 93.2 kg N ha-1 was removed in the DM with the best NUE and NRE at the lower fertilizer rates. High biomass sorghum could potentially reach optimum yields in Missouri with minimal fertilizer inputs.